Airscrew having a variable pitch



NOV. 29, 193 8. I CHAUVIERE 2,1385339 AIRSCREW HAVING A VARIABLE PITCH Filed June 17, 1936 10 Sheets-Sheet lv Pic-3.1.

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\NVENTOR= LUCIEN EDOUARD CHAUVIERE BY #Amm ATTORNEYS L. E. CHAUVIERE- AIRSCREW FIAVING A VARIABLE PITCH Filed June 17, 1936 l0 Sheets-Sheet 2 mam EDOUAR CHAUVIERE ATTORNEYS Nov. 29, 1938. E. CHAUVIERE 2,138,339

AIRSCREW HAVING A VARIABLE PITCH Filed June 17, 1956 10 Sheets- Sheet I5 Pic-3. 2.

- ATTORNEYS \NVENTOR:

'AIRSCREW HAVING A VARIABLE PITCH Filed June 17, 1936 10 Sheets -Sheet 4 \NVENT/OR; LUCIEN EDOUARD CHAUVIERE Nov. 29, 1938.

L. E. CHAUVIER'E 2,138,339 A IRSCR EW HAVING A VARIABLE PITCH Filed June 17, 1956 10- Sheets-Sheef 5 INVENTOR= 'LUCIEN EDOUARD CHAUVI'ERE ATTORNEYS 1 Nov. 29, 1938. c uv E 2,138,339

AIRSCREW HAVING A VARIABLE PITCH Filed June 17, 1936 10 Sheets-Sheet 6 Fig.3 a.

I INVENTOR LUCIEN EDOUARD CHAUVIE RE ATTORNEYS Nov. 29, 1938. 1.. E. CHAUVlERE AIRSCREW HAVING A VARiABLE PITCH l0 Sheets-Sheet '7 Filed June 17, 1936 \NVENTOR LUCiEN EDOUARD CHAUVIERE ATTORNEYS AIRSCREW HAVING A VARIABLE PITCH Filed June 17, 1936 10 Sheets-Sheet 8 IHVENTOm LUCIEN EDOUARD CHAUVIERE ATT'o RNE Y5 Nov. 29, 193s.

L. E. CHAUVIERE 4 2,138,339

AIRSCREW HAVING A VARIABLE P ITCH Filed June 1 7, 1936 10 Shets-Sheet 10 \NVENTOR LUCIEN euoumo .ATTQRNEIS CHAUVIE RE Patented Nov. 29, 1938 UNITED STATES PATE'NT OFFICE 2,133,339 AIRSCREW HAVING A VARIABLE rrrcn Lucien Edouard Chauvire, Paris, France, as-

signor to Socit Anonyme: Forge et Usinage de Mtaux Lgers (Hlices Mtalllques Chauvirc) Vitry-sur-Seine, France Application June 17, 1936, Serial No. 85,757 v In France June 20, 1935 10 Claims. (Cl. 170-163) The present invention relates to an improved air-screw, the pitch of which may be varied during flight, and of the type in which the variation of the pitch of the blades is controlled by the rotation of the airscrew itself, employing an intermediate system of the epicyclic type combined with braking means and effecting the driving of devices, such as worms and worm gears directly controlling the inclination of the blades.

The technical problem, for which a solution is given by the present invention, consists in ensuring a great stability andthe locking of the blades on the hub in all positions, while automatically limiting the amplitude of the variations of the pitch to predetermined values without risk of damaging the driving members.

The airscrew. according to the invention is characterized in that the transmission of movement to the devices controlling directly the inmesh with a ring gear actuated through the medium of rockingmembers pivoted to said ring gear and having nose portions adapted to engage grooves in a ring gear constantly in mesh with one of the sets of teeth of double plane pinions whereof the other set of teeth is in engagement with the teeth of a driving gear keyed to theshaft of the airscrew, this assemblage forming an epicyclic system. The movable equipment of this epicyclic system is connected, on the one hand, rigidly to the first of a pair of drums and, on the other hand, through the medium of gears driven by said driving gear, to the second or idle drum. The inclination of the blades is varied in one direction or the other by applying a brake to one or the other of the drums.

In a form of construction, the improved airscrew comprises three units, firstly the hub and the devices controlling directly the inclination of the blades, secondly a casing enclosing all the gears and mechanisms and, thirdly, a relay allowing the pilot to control the brake from a distance.

These three units are substantially separate, which greatly facilitates the assemblage, 'adJust ment, inspection and replacement of certain parts.

According to a particularly important feature of the invention, the rocking members, for driving the ring gear meshing with the pinions actuating the devices directly controlling the inclination of the blades, are combined with abutments acting as cams which render these rocking members inoperative in order -to limit the displacewhich:

merits of the blades independently of the actuating mechanism.

Preferably two locking members acting respectively in one direction and in the other are used in combination with two pairs of abutments acting as earns; the first pair limiting the displaceextended to the limits set by the second pair.

The invention further relates to other particular points which will appear from the following description, with reference to the accompanying drawings, given by way of example only, and in Fig. 1 is""an axial longitudinal section of a variable pitch airscrew according to the invention, this section being made according to line I--I of Fig. 2.

Fig. 1a is a section of a modification along a line which corresponds only with the line I--I of Fig. 2.

Fig. 2 is a" left-hand side view corresponding to Fig. 1, with section made according to line IIII of this figure.

Fig. 2a is a rear view of the brake mechanism illustrated in Fig. 1. v

Fig. 3 is a section made according to line II I-III of Fig. 1.

Fig. 3a is a section made according to line IIIA--IIA of Fig. '1'.

Fig. 3b is a section made according to line lIIB-IIIB of Fig. 1.

Fig. 3c is a perspective view showing'the assemblage and operation of the pawls more particularly illustrated in Figs. 3 and 3a.

Fig. 4 is an elevation, with partial axial section, of a form .of construction of a control device.

Fig. 5 is a section'made according to line V-V of Fig. 4.

Fig. 6 is a front view of the manual control device arranged on the instrument board of the pilot. i v

'Fig. '1 is an axial longitudinal section of another form of construction of a variable pitch airscrew according to the invention.

Fig. 8 is a corresponding front view.

Fig. 9 is a crosssection of the control device illustrated in Fig. 7, this section being made on through the medium of ball bearings 3.

an enlarged scale according to line IXIX of said Figure 7.

The airscrew the pitch oi! which is variable during flight, and more particularly illustrated, comprises two blades the roots l of which are fitted into corresponding arms of the hub 2 which is rendered angularly rigid with the driving shaft-2 The roots i of the blades are so fitted up as to be capable of rotating and they bear upon an inner shoulder 2 of the hub 2 The roots I are rendered rigid with worm gears 4 through the medium of teeth or flutes l provided on the gears 4 and of flutes l provided on the periphery of flanges I! formed at the ends of the roots i. These flutes I" and I flt into each other for rotatively connecting the roots I and the worm gears 4. Each worm gear 4 is actuated by a worm 5, cut in a shaft 5* one of the ends of which is fluted at 5 for fitting into corresponding flutes 5 provided with pinions 8. These latter are journalled in bearings 8' rigid with a member I, constituting a casing for the control box and which is rendered angularly rigid with the driving shaft 2. The number oi pinions 8 is equal to that of the worms 6, thesepinions constantly meshing with a gear l0. Moreover,

the pinions 8 are held stationary in translation on the bearings ll by nuts or rings 9 mounted on the ends of the pinions arranged outside the casing I.

On the gear l0 are pivoted, through the medium, of pins-ii, two rocking or looking memments 29 and 3| acting as cams.

The two abutments 29 are adjustable in posiextreme positions of the blades, for placing the latter for instance in the winds eye position or in a braking position.

The two abutments 3i are adjustable in position in an arcuate slide 3| and allow of limiting the position of the blades for instance for cruising flight and for taking off.

For allowing both rocking or looking members i2 to pass beyond the two positions limited by the two abutments 3| and for causing the abutments 29 to act if desired, thetwo abutments 3| can be retracted. For that purpose, use is made oi. a roller 32 joumalled on a lever 32 provided with an extension for receiving a counterweight 32 adapted to' balance centrifugal force.

The lever 32 is rigid with a stud 33 journalled in a support 33 secured on the member I. On the stud 33 is secured a lever 33,. the nose or which engages with a .lever 34 rigid with a. stud 34 journalled in member I. The shaft 34 is rigid with a lever 34 carrying the arcuate slide 3|. for the abutments 3|. It will be noted that the arcuate slide 29 for the abutments ,23, is provided in member I.

The lever 33 is constantly urged in the required position for locking lever 34- and, consequently,-

lever 34, through the medium of a spring 33 wound on the stud 33*.

For releasing lever 34*, the roller 32 is acted upon through the medium of a cam 32 pivoted about a fixed pin 32* in order to move the lever 32 in the direction of the arrow F. Conse- ,tion, in an arcuate slide 23 and can limit the 7 reverse directions.

. shown in Fig. 3a.

quently, the lever 33 moves in the direction of the arrow F in, antagonism to the action of the spring 33 and by disengaging from lever '34, so that the rigid unit formed by lever 34*,

shaft 34 and lever 34 is released.

Under the action of centrifugal force, the lever rotates with its shaft 34 and the lever 34 in the direction of the arrow F, in order that the abutments 3| should no longer be situated in the path of the heel pieces of the rocking members l2.

When the blades return towards their normal position, the lever 34 and, consequently, lever 34, as well as the abutments 3! are automatically restored to the position shown in Fig. 2 by a finger 35 acting as cam. In fact, the finger 35, which is tapered at one end for constituting a cam, is moved in translation in the direction of the arrow F by a cam 36 (see also Fig. l) belonging to the ring gear l0, this finger being restored, to its position of rest as soon as the cam 36 ceases to act thereon, by a spring 35". The cam 36 acts, in the same manner for both abutments 3i and its action can'be exerted in both directions for moving in translation the finger .35 in the direction of the arrow F The action of this finger 35 which is positively controlled by cam 36 compels lever 34' and, conse quently lever 34, to return to its position shown in Fig. 2, in antagonism to the action of centrifugal force. As at this moment cam 32 no longer acts on roller 32, the unit formed by arm 32% and arm 33 returns, under the action of spring 33 to the position of Fig. 2 for locking lever 34 as shown in this Fig; 2. The lever 34 is then automatically locked by the nose of lever .33, the roller 32 being no longer subjected to the action of. cam 32'. The finger 35 is constantly urged to retracted position by a spring 35 and it is moved in' the direction of the arrow F by a cam 36 provided on gear ID, as indicated. The gear I3 is provided, independently oi the flutes l3 with teeth l3 with which constantly mesh the double planet pinions l5 iournalled in a crown l1 loosely mounted on sleeve l3. The planet pinions l5 also mesh with a gear [4 rendered rigid with the driving shaft 2'.

The gear ratios of both'sets of gears i5 and H on the one hand, and l5, l3 on the other hand, are but very slightly diflerent so as to give a very high gearing down ratio.

The crown i7 is kinematically connected to a co-axial crown or drum 2| loosely mounted through the medium of planet pinions 31 rigid with the double planet pinions l5.

Fig. 1a shows a constructional modification of Fig. l. The description of Fig. 1 is entirely applicable to Fig. 1a, except concerning the double planet pinions l5 and the planet pinions 31. In the case of Fig. la, on the crown II is rigidly secured, by means of bolts 24", a. bevel gear- 24'. In this form of construction, the crown I1 is kinetmatically connected to the coaxialcrown or drum 2| loosely mounted through the medium of bevel pinions 24 which are constantly meshing with the bevel gear 24- and corresponding teeth provided on the drum 2|.

For obtaining small variations of the pitch of thebIades, as'will be indicated later on, use can be made or two pawls I9 and l9' arranged in The pawl l3 is more particularly illustrated in Fig. 3, and pawl |3' is The pawl 19 can act on ratchet teeth ll provided on crown I'|,.whilst the pawl I3 can act on ratchet teeth il also 7 provided on crown II. The teeth I'I are set in reverse directions.

The pawls I and I8" are respectively pivoted about shafts I9 and I0. These shafts are respectively rigid with bell crank levers I0' --I0 and I0"--I9 respectively pivoted about fixed shafts I9 and I9" mounted on member I, through the medium of bearings I9 forming supports.

The branches I0 and I9" of bell crank levers project outside the member or casing I through apertures I9 so that they can be moved, for branch IS, in the direction of the arrow FI9 and, for branch I9", in the direction of the arrow FI9' through the medium of movable cams 30 and 30, respectively. The pawls then come in position, as shown in dot and dash lines in Figs. 3 and 3a, for anguiarly moving the crown H to the extent of one tooth in the direction of the and I1 arrow J, or of the arrow I, according as the pawl I9 or the pawl I9 is acted upon;

It is possible to limit the amplitude of the displacements imparted to the crown I1 by the pawls. For that purpose, cams are provided which are rigid with the gear I0 and can be adjusted in position. In the example illustrated in Figs. 1, 2, 3, 3a-,'3b and 3c. the cams 28 mounted on gear I0 act on projections I0 or I9 of the pawis I9 and I9' for causing lifting of the noses of the pawls which no longer act on the corresponding teeth I1 and I'l of the crown I1. Moreover, a brak-' ing device 28 can be interposed between the member or casin 'I and the crown I'I, this braking device comprising a friction crown 28' urged against the crown H by springs 28.

The crown wheels or drums I1 and 2I can be held stationary separately, but not simultaneously, by a brake I8 controlled, in one direction or the other, by a lever 21.

As more particularly illustrated in Fig. 2a, the two segments I8 constituting the brake I8 are pivoted about a common shaft I8 and respectively about shafts I8 and li mounted on the control lever 21.

The brake I8 is fitted on the engine casing and the displacement of the lever 21 is efiected from a distance, either by means of Bowden cables and handles, or, as illustrated in Figs. 4, and 6, by means of two fluid-tight pistons 38 moving in cylinders 30" into which is admitted a compressed fluid, such as air.

For controlling the admission or exhaust of compressed air, use can be made of any suitable means arranged within reach of the pilot. Fig. 4 shows a control cock provided with a slide or port face l0 on which is always pressed, by the pressure, a rotary valve 39, the cock body being indicated at 40. An arcuate groove 30', provided in the rotary valve 30, allows exhaust of the cylinder to take place at dead center, or the exhaust of a cylinder to take place when the other is under pressure, exhaust taking place through a channel 50 provided in the cock body 40. Onthe latter are fitted two intakes 5i and 02 respectively communicating with the bottoms 53 and M of cylinders 38-, these intakes being respectively in communication with channels 5i and 52'- provided in the body 40, and controlled by the rotary valve 33. The latter is provided with a port such as 55 for allowing the admission,

in either of channels BI, 52, of air under pressuresupplie'd by a channel 56. The rotary valve 30 is rigid with a lever 80 restored to mean position by a spring ii, the displacements of this lever being limited by abutments such as 02.

antagonism to the compression of one or the other of the ends of the spring, compression which automatically restores the lever to its initial position, as soon as it is no longer acted upon. The lever 30 is actuated by a rocking member 04 .rigid with the manual control 05.

The lever 21 is provided with arod 08 to which are pivotally connected rods I0 and 'II of the piston 38.

The operation of the airscrew having a variable pitch during flight and which has just been described in its main lines is the following:

When the pilot desires to modify the pitch of the blades he acts on the rotary distributing the valve 30 through the operating lever, by actuating the same in one direction or the other, according to the desired direction of modification of the pitch. 4

The compressed air admitted into one of the cylinders 38', acts on brake I0 which prevents crown or drum 2I, or crown or drum H from rotating. The wheel or gear I4, which angularly moves with the driving shaft 2* causes the rotation of the planet pinions I5 which determine a slow rotary movement of gear I3 relatively to the driving shaft 3". This wheel or gear I3 drives. through the medium of the locking or rocking members l2, the gear I0 on which these members are pivoted. The relative displacement of this gear I0 causes the rotation of pinions 8, and, consequently, of the worms 5, worm gears 4 and finally of the blades. The blades can obviously be stopped in any desired intermediate position by ceasing to act on the operating lever 85. Any suitable indicating device can moreover be provided allowing the pilot to control the exact position of the blades.

If the pilot continues to act on lever 85, the pawl I2, which is in action, finally comes in engagement with one of the abutments 3i which renders it inoperative, the blades are then held stationary in the cruising or taking off position, these abutments 3| being adjusted for that purpose.

As previously indicated, the abutments 3i can be rendered inoperative by moving the cam 32; in this case, the abutments 20 limit the displace- .ment of the blades, either to the winds eye position, or to the braking position.

An extremely slow displacement of the blades can also be ensured by acting on the cams 30 and 30', as previously indicated.

In any position in which the blades are stopped, the latter are locked in position owing to a control effected by means of an irreversible device constituted by the worms 5 and worm gears l, as well as by the planet-pinion reducing gear which is also irreversible.

Another form of construction of an airscrew the pitch of which is variable during flight is more particularly illustrated in Figs. 7, 8 and 9. This airscrew comprises wooden blades I fitted in sockets I00 of reinforced construction.

These blade roots each comprise a tubular part IOI externally screwthreaded at I02.

Referring to Fig. '7, it will be seen that the roots I00 are screwed in corresponding members I05 so formed as to constitute the worm gears 4.

Thrust bearings are providedat I06 and needle bearings at I01. The roots I00, rigid with the corresponding members I05, are fitted up as illustrated for rotating under the action of the worms 5 meshing with the worm gears 4, these worms being rendered angularly rigid with the pinions 8 constantly meshing with a gear Iii provided with a side groove for receiving the looking or rocking members l2 pivoted about pins l I rigid with the gear l0. These actuating locking or rocking members l2 are directed in reverse directions and the noses can engage with grooves l3 provided in a gear I3 loosely mounted on a sleeve i3 surrounding the hub i of member I.

This member 1 is rigidly secured on the hub 2 of the airscrew and carries the pinions 8. The locking members l2 can be rocked for releasing the noses from the flutes I8, when their heel pieces come in contact with the abutments 3i when the latter serve as cams. Both abutments 3| are adjustable in position in an arcuate slide 3i of member 1 and allow, as in the first form of construction, of limiting the position of the blades for instance for cruising and for taking off. The gear I5 is provided, independently of the flutes I 3 with teeth i3 with which constantly mesh the double planet pinions l5 journalled on a loose crown wheel I! constituting a drum II The'planet pinions I5 also mesh with a gear I! rendered rigid with the driving shaft. The gear ratios of both sets of gears l5, H on the one hand, and l5, l3 on the other hand, are but very slightly different so as to give a very high gearing down ratio.

Planet pinions I20, co-axial with planet pinions i5 and rigid with the latter, are journalled on the crown l1 and constantly mesh with a gear i2l rigid with a drum 2!.

As in the first form of construction, the braking, either of drum li or of drum 2|, allows the moving of the blades either in one direction or the other.

It is obvious that the form of construction described and illustrated is given herein by way of indication only and not in a limiting sense. Any changes or modifications which do not alter in any way the main features above set forth and the desired result, remain included in the scope of the present invention.

It will be noted that, according to a very important feature of the present invention, the transmission of movement to the devices directly controlling the inclination or change of pitch of the blades, is eifected through pinions 8 iournailed in a box I rigid with the hub of the airscrew. These pinions 8 constantly mesh with a gear l controlled by means of rockers I 2, pivoted on this gear l0 and the noses of which can enter flutes l3? provided in a fluted gear IS. The tter constantly meshes with one set of teeth of planet pinions l which have two sets of teeth, the other set of teeth meshing with the teeth of a driving gear i4 rigidly secured on the shaft of the airscrew, the movable unit of the system of the epicyclic type thus constituted being rigidly connected, on the'one hand, to a flrst drum I 1 and, on the other hand, through the medium of gears driven by said driving member, to a secand loose drum 2|.

Moreover, the ratios ofthetwo sets of gears constituted, on the one hand, by the fluted gear 13 provided with flutes for the actuation of the rockers l2 and the corresponding set of teeth of the planet pinions l5 and, on the other hand, by the teeth of the driving member I and the other set of the teeth of the planet pinions ii, are but very slightly different so as to give a very great gearing down ratio and to ensure the locking of rotatably controlled by the rotation of said airscrew for modifying the pitch of said blades, in combination: a casing rigid with said hub, pinions journalled in said casing and so shaped for meshing and being rendered rigid with the ends of said worms, a ring gear iournalled in said casing co-axial to said hub and meshing with said pinions, so that the movement of rotation of said ring gearin said casing determines the rotation of said pinions, a fluted gear journal led coaxial to said hub and so shaped as to present a set of teeth, rockers pivoted on said ring gear, reversely arranged and so shaped as to constitute noses fitting in said flutes of the fluted gear for r rendering it rotatably rigid with said ring gear, means effective upon attainment of predetermined limiting values of pitch to move said rockers out of engagement with said flutes, a member fast on the airscrew hub for constituting the driving gear, said member being so shaped as to present a set of teeth, a flrst drum Journalled on said hub, gears Journalled in said flrst drum and meshing, on the one hand, with the teeth of the fluted gear, and, on the other hand, with the teeth of the said driving gear for kinematically connecting with the driving gear, said fluted gear, a seconddrum loosely mounted on the hub, means for kinematically connecting the second drum with the last mentioned gears, means for braking one or the other of the drums but not simultaneously for causing the rotation of said fluted gear in one direction or the other and, consequently, through the medium of the rockers, that screw formodifying the pitch of said blades, in-

combination: a casing rigid with said hub, pin ions joumalled in said casing and so shaped for meshing and being rendered rigid with the ends of said worms, a ring gear journalled in said casing co-axial to said hub and meshing with said pinions, so that the movement of rotation of said ring gear in said casing determines the rotation of said pinions, a fluted gear journalled co-axial to said hub and so shaped as to present a set of teeth, rockers pivoted on said ring gear, reversely arranged and so shaped as to constitute noses fitting in said flutes of the fluted gear for rendering it rotatably rigid with said ring gear, means efl'ective upon attainment of predetermined limiting values of pitch to move said rockers out oi! hub, double planet pinions or having a double set of teeth, the first set of teeth of which meshes with the teeth of said fluted gear and .the second set of teeth of which meshes with the teeth of the driving gear, 'a second drum loosely mounted on the hub and so shaped as to present a gears rigid with said double planet pinions and meshing with the teeth of the second drum, means for braking one or the other of the drums but not simultaneously for causing the rotation of said fluted gear in one direction or the other and, consequently, through the medium of the rockers, that of the ring gear controlling the pinions fast on the worms meshing with the worm gears fast on the blades for modifying the pitch ofth'e latter in one direction or the other.

3. In a variable pitch airscrew as claimed in claim 1, the ratios of the two sets of gears constituted, on the one hand, by the ring gear and the first set of teeth of the double planet pinions and, on the other hand, by the teeth of the member forming the driving gear and the second set of teeth of the double planet pinionsare but very slightly different so as to produce a very high gearing down ratio and lock the blades through the medium of the double planet pinions, in each position at any given pitch,

4. In a variable pitch airscrew as claimed in claim 1, both drums are co-axial in order to provide between them an annular space in which the braking means are arranged, said braking means comprising brake segments capable of acting, on either one of the drums, either by being drawn together or by being spaced apart.

5. In a variable pitch airscrew as claimed inclaim 1, means for controlling from the pilots seat, the means for braking the drums.

6. In a variable pitch airscrew comprising a hub, blades rotatably mounted in said hub, worm gears rigid with the roots of said blades, worms meshing with said worm gears, said worms being rotatably controlledby the rotation of said airscrew for modifying the pitch of said blades, in

combination: acasing rigid with said hub, pinions journalled in said casing and so shaped for meshing and being rendered rigid with the ends of said worms, a ring gear journalled in said casing co-axia'l to said hub and meshing with said pinions, so that the movement of rotation of said ring gear in said casing determines the rotation of said pinions, a fluted gear journalled co-axial to said hub and so shaped as to present a set of teeth, rockers pivoted on said ring gear, reversely arranged and so shaped as to constitute noses fitting in said flutes of the fluted gear forrender ing it rotatably rigid with said ring gear, means effective upon attainment of predetermined limiting values of pitch to move said rockers out of engagement with said flutes, a member fast on the airscrew hub for constituting the driving gear, said member being so shaped as to present a-set of teeth, a first drum journalled on said hub, double planet pinions having a double set of teeth the firstset of teeth of which meshes with the teeth of said fluted gear'and the second set of teeth of which meshes with the teeth of the driving gear, a second drum loosely mounted on the hub and provided with a set of teeth, toothed pinions journalled on the driving gear and meshing with the teeth of the second drum, 2. bevel inion in' the shape of a crown rigid with the first set of teeth,-

drum and meshing with said toothed pinions, means for braking one or the other of the drums but not simultaneously for causing the rotation of said fluted gear in one direction or the other and, consequently, through the medium of the rockers, that of the ring gear controlling the pinions fast on the worms meshing withthe worm gears fast on the blades for modifying the pitch of the latter in one direction or the other.

7. In a variable pitch airscrew as claimed in claim 6, the ratios of both sets of gears constituted, on the one hand, by the fluted gear and first set of teeth of the double planet pinions and,

to the position of the pitch forcruising flight orof the pitch for taking oil, a first pivoted lever adjustably carrying said first pair of abutments, said lever terminating in a finger, a. second pivoted lever provided with a roller, and with .a

counterweight and having one of the ends thereof formed into a hook for said finger, a pivoted cam capable of being moved by control means from the pilots seat into thepath of said roller for'rocking the secondlever and releasing the first lever and causing same to move outwardly under the action' of centrifugal force in order to shift said first pair'of abutments from the path of the rockers, a tapered finger capable of'being moved by a projection of the ring gear and which can restore the locking finger and, consequently, the first lever to its initial position, and a second pair of cams adjustably mounted for rendering. the rockers inoperative when the first pair" of abutments is rendered inoperative, this second pairof abutments acting as cams limiting the displacements of the blades to the featheringposition or braking position.

9. In a variable pitch airscrew as claimed in claim 1,-in combination: pawls pivoted on the casing and set in reverse directions, the first drum on which the double planet pinions are journalled being so shaped as to prevent two sets of ratchet teeth set in reverse directions and on which the pawls act, and cams controlled from the pilots seat so as to be shifted into the path of the pawls for moving the drum tooth by tooth, either in one direction or in the other. 9

10. In an installation for avariable pitch airscrew as claimed in claim 1, the braking means are controlled from the pilots seat through the medium of means comprising in combination, a source of fluid underpressure, a cylinder, two pistons movable in translation in said cylinder, means for connecting said pistons to said means for braking the drums and a distributor for controlling the admission and escape of a compressed fluid admitted in said cylinder, amultiway cock for controlling the admission of the fluid under pressure between said source and the cylinder and for controlling the escape of said fluid.

' LUCIEN EDOUARD CHA 

